1. Field of the Invention
The present invention relates to a stranded conductor to be used for movable member and a cable using the same, and particularly to a stranded conductor to be used for movable member, for which high strength, high flexing properties, and high conductivity are required as well as to a cable using the stranded conductor to be used for movable member.
2. Description of Related Art
In recent years, a cable used as a wiring material for movable member such as medical instruments, industrial robots, and electronic equipment such as notebook-size personal computer and the like, for instance, a cable used for medical equipment is applied under an atmosphere where an external force produced by combining severe bending, twisting, tensile and the like forces with each other is loaded repeatedly in medical field. For this reason, such a cable conductor is required to have excellent characteristics in tensile property (tensile strength) and flexing properties (elasticity, and torsibility).
Furthermore, it is intended to make a diameter of a conductor more slender with respect to a request or a demand for downsizing and weight reduction of electronic equipment and the like. However, tensile properties and flexing properties decrease with decrease in a diameter of a conductor. Thus, there is a fear of arising breaking of wire in an early stage during use of equipment due to buckling, fatigue and the like.
Moreover, since a frequency of transmission signal is in a GHz level with increase in an amount of information to be transmitted with respect to a cable conductor used in electronic equipment and the like, transmission characteristics in a high-frequency band (hereinafter referred to as xe2x80x9chigh-frequency propertiesxe2x80x9d) are considered to be important.
In order to cope with such request and demand as described above, the following cable conductors have been developed. (1) A cable conductor prepared from a copper alloy material wherein Sn, Ag or the like is added to copper, whereby tensile properties and flexing properties thereof have been elevated. (2) A cable conductor prepared by incorporating stainless wires or fibrous interposition inside a strand made from a high conductive copper material such as soft copper (this means herein a generic term for a copper material prepared from electrolytic copper, deoxidized copper, oxygen free copper or the like) as a tension member. (3) A cable conductor prepared by disposing an element wire having a high strength on the outer layer of a strand made from a high conductive copper material such as soft copper.
In a conductive material constituting a cable conductor, antithetical characteristics are required. Namely, good conductivity (high conductivity) as well as good tensile and flexing properties are demanded at the same time. In this respect, however, although tensile and flexing properties can be improved by increasing an amount of an additive to be added to copper in the cable conductor (1), there has been a problem of lowering conductivity with increase of the additive. In this case, it is possible to control tensile properties and conductivity within a range of a certain degree by adjusting an amount of an additive. However, when elevation of flexing properties is intended, it results in remarkable reduction in conductivity. Hence, there has been a problem of giving rise to reduction of high-frequency properties.
Furthermore, it is an important factor that a connecting section of a cable conductor has such a conductor structure, which is compact, connection of which is easy, and reliability in connection is high with a trend toward downsizing of electronic equipment and the like. In this respect, there have been problems of reduction of workability in stranding operation, remarkable reduction of conductivity, and reduction of terminal processability (connecting properties in case of processing a terminal by means of soldering, contact-bonding or the like operation) with respect to the cable conductor (2), when it was formed into an extra fine wire having an outer diameter of 0.08 mm or less.
Moreover, the cable conductor (3) is comparatively excellent in flexing properties, while there has been such problem that high-frequency properties are not good.
In view of the circumstances as described above, an object of the present invention is to provide a stranded conductor to be used for movable member having good stranding workability and terminal processability as well as having good conductivity, tensile properties, flexing properties, and high-frequency properties, and to provide a cable using the above-described stranded conductor.
In order to achieve the above-described object, a stranded conductor to be used for movable member according to the present invention prepared by stranding two or more types of element wires with each other, each type having different mechanical properties from one another, and having a two-layered structure of an inner layer section and an outer layer section, comprises a first element wire constituting at least the inner layer section having 1.5 times or higher tensile strength than that of a second element wire constituting at least a part of the outer layer section; and the respective element wires being stranded with each other in such that a ratio of a strength in a group of inner layer element wires forming the inner layer section to a strength in a group of outer layer element wires forming the outer layer section (a tensile strength in the group of inner layer element wires/a tensile strength in the group of outer layer element wires) comes to be 0.5 to 5.
Furthermore, a stranded conductor to be used for movable member according to the present invention prepared by stranding two or more types of element wires with each other, each type having different mechanical properties from one another, and having a two-layered structure of an inner layer section and an outer layer section, comprises a first element wire made from a rigid copper alloy wire having 1000 MPa or higher tensile strength and 0.2% or higher elongation, which constitutes at least the inner layer section; a second element wire made from a soft or a semi-rigid copper alloy wire having 70% or higher IACS and 5% or higher elongation, which constitutes at least a part of the outer layer section; and the respective element wires being stranded with each other in such that a ratio of a strength in a group of inner layer element wires forming the inner layer section to a strength in a group of outer layer element wires forming the outer layer section (a tensile strength in the group of inner layer element wires/a tensile strength in the group of outer layer element wires) comes to be 0.5 to 5.
According to the above-described constitutions of the present invention, since second element wires each having high elongation are disposed for an outer layer section having the highest amount of strain, and a first element wire(s) is (are) arranged for an inner layer section to which the highest tensile stress is to be loaded, good tensile properties are obtained, besides a remarkable improvement in flexing properties can be intended. Moreover, since the second element wires constituting the outer layer section exhibit high conductivity, high frequency properties of the resulting stranded conductor become good.
On one hand, a cable using a stranded conductor to be used for movable member according to the present invention comprises an insulating layer being disposed around the outer circumference of the above-mentioned stranded conductor to be used for movable member.
According to the above-described constitution of the present invention, a cable having good stranding workability and good terminal processability as well as having good conductivity, tensile properties, flexing properties, and high-frequency properties can be obtained.